The invention relates to systems for electronic control of light sources and more particularly to a microprocessor-driven system for automatically controlling and varying the intensity of vehicle signal lights used for signalling drivers of following vehicles to show braking and deceleration.
For a number of decades it has been conventional practice for domestic and foreign producers of vehicles to equip them with dual light sources, referred to as brake lights, to signal the application of brakes. Such brake lights are used for reasons of safety, and are required by regulatory authority in this and other nations.
More recently, regulatory authority has promulgated, in the interest of safety, the implementation of vehicle center-mounted brake light signals which are thus physically separated from vehicle running lights in order that following drivers might more promptly and reliably be able to gain greater perception of the application of brakes in a vehicle so equipped.
Brake lights, as today used in the automotive industry, whether mounted in conventional pairs or center-mounted, do not conventionally indicate more than that the vehicle operator has applied brakes; and indeed it has been conventional for many decades simply to energize the brake lights from the vehicle electric power source in response to closure of a switch operated either by movement of a brake mechanism (e.g., pedal) or by increase in pressure of hydraulic fluid used to directly activate brake devices. Thus, brake lights conventionally are switched either on or off without modulation of intensity.
Nevertheless, it has long been proposed in the patent and other technical literature to vary brake light intensity or switching rate (e.g., by flashing action) as a function of brake pressure or as a function of the magnitude of deceleration brought about by braking. The use of various inertia-responsive devices such as springs, decelerometers, and pendulums has been proposed in the literature for responding to vehicle rate of negative acceleration. U.S. Pat. Nos. 2,474,610; 3,089,129; 3,157,854 are instructive in that regard, as are more recent U.S. Pat. Nos. such as 4,357,594; 4,258,353; and 3,875,559. U.S. Pat. Nos. 3,538,496; 3,665,391; and 3,593,278 may also be noted as illustrative of the state of art.
In general, such art may be characterized as relating either to (a) devices of type for varying brake light intensity as a function of a parameter (e.g., deceleration), or to (b) devices of types for varying a flash rate as a function of some such parameter. The present invention relates to devices of type (a).
Recent U.S. Pat. No. 4,952,909 as well as U.S. Pat. No. 4,357,594 are both to be noted as relating to the use of microprocessor circuitry for brake light control in response to deceleration or velocity, even though said U.S. Pat. No. 4,357,594 is a device of type (b) insofar as there is proposed therein control only of blink rate of a warning indicator in proportion to a degree of hazard sensed according to change in deceleration, brake pressure, motion or speed thereby to alert a following driver to a potential hazard. Recent U.S. Pat. No. 4,958,143 teaches combining a conventional brake light with a flash lamp thereby to alert a following driver simply of the application of brakes.
Freeman et al U.S. Pat. No. 4,231,013 of present inventor W. H. Freeman and another teaches a concept of controlling the duty cycle of a pulse-form signal provided for energization of vehicle brake lights for purposes of controlling brake light intensity in stepwise manner as a function of brake pressure. The present invention is deemed to be an improvement over the system of such patent.